A recent study by Farallon Institute scientists examined the collapse of the anchovy population in California, which appeared to be unrelated to fishery effects. We developed new estimates of abundance of northern anchovy (Engraulis mordax) from egg and larval densities for the period 1951-2011 in the Southern California Bight. Previous estimates utilizing mean density over the area have a bias because of the nearshore concentration of CalCOFI sampling stations and the anchovy population tendency to contract into that area when abundances are low. We developed total egg and larval population estimates for January and April, formed a combined ichthyoplankton index, and calibrated it to the absolute biomass estimates produced by the Daily Egg Production Method in the early 1980s. Anchovy spawning biomass was very low, near 10,000-20,000 tons, in the early 1950s when CalCOFI sampling began. Abundance then increased and fluctuated between 0.5 and 2 million tons from 1960 through 1990. After 1990, spawning biomass fluctuated around 200,000 tons, briefly increased dramatically in 2005-2006, then declined drastically over four years to below 20,000 tons in 2009-2011. CalCOFI Bongo net samples collected after 2011 are not yet available for analysis, but the continuous underway egg sampling conducted during CalCOFI cruises indicated continued low abundance through 2015.
This remarkable decline in anchovy abundance occurred in the absence of a significant fishery. Present annual catches of a few thousand tons are small by historical comparison, but the exploitation rate may now be relatively high given the low stock abundance. The decline in anchovy abundance also coincides with recent reports of die-offs and reproductive failures of top predators that rely on anchovy for food.
This research was described in a recent article in the journal Fisheries Research.